Compositions having isocyanate functional components are utilized to bond substrates together. One common use of such compositions is to bond glass, often in the form of windows, into structures. In automotive assembly plants windows are often bonded in with one part adhesive compositions containing isocyanate functional components. Typically these compositions cure by reaction with ambient moisture. One part adhesives are used because the equipment required to dispense and apply the adhesives is less complex than the equipment used to apply two-part adhesive compositions. The one part moisture curing adhesives typically take several hours to cure. In the assembly plant environment, vehicles are not driven for several hours and this slow curing process is acceptable. One part moisture curing adhesives known in the art are disclosed in U.S. Pat. Nos. 4,374,237; 4,687,533; 4,780,520; 5,063,269; 5,623,044; 5,603,798; 5,852,137; 5,922,809; 5,976,305; 5,852,137 and 6,512,033, relevant portions incorporated herein by reference. Examples of commercial one part adhesives include BETASEAL™ 15630, 15625, 61355 adhesives available from The Dow Chemical Company, EFBOND™ windshield adhesives available from Eftec, WS 151™, WS212™ adhesives available from Yokohama Rubber Company, and SIKAFLEX™ adhesives available from Sika Corporation.
Two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components in the other part are used in situations where cure speed is important. One such environment is in the automotive aftermarket replacement glass business. Often customers desire that the adhesives cure quickly so that the vehicle can be driven as soon as possible after bonding of the replacement window into the vehicle. The advantage of a two-part adhesive is that the curing reaction proceeds at a much faster reaction rate than does a one part moisture curing adhesive system. Examples of two-part compositions containing isocyanate functional compounds or prepolymers in one part and compounds and/or prepolymers having isocyanate reactive components in the other part are disclosed in EP 1,524,282, U.S. Pat. Nos. 5,852,103; 6,709,539; 7,101,950 and 7,361,292, relevant parts incorporated herein by reference. Some of these two part compositions were developed to allow automobiles with replacement windows to be driven within 30 minutes of bonding the window into the automobile. Some of these adhesives have achieved commercial success. Nevertheless the installers and customers demand even faster systems such as systems that can allow the automobiles to be driven 15 minutes after installation.
Adhesives are utilized in a variety of environments and the properties required in different environments are different. It is desirable that adhesive systems be developed that allow for modification of properties of the cured adhesive to fit the environment of use or the substrates bonded. For instance modification of the relative elasticity and modulus of adhesive is desirable. Often manufacturers desire to handle products as soon as possible to enhance the productivity of their plants. In modern industrial processes, there is a need to move parts and to place, loads on adhesive systems as soon as possible. Thus, adhesives which have a good green strength shortly after application are needed. Typical one part adhesives do not provide such green strength properties. Further, the adhesive systems need a longer open time, the time from application of the adhesive to a substrate until the adhesive can no longer adhere to another substrate, than a typical two-part adhesive allows. An open time of between 8 minutes and 15 minutes is desired. Thus, installers desire fast drive away time and a longer open time to adjust the placement of the window in a vehicle.
Thus, what is needed is an adhesive system which exhibits good green strength, rapid cure rates and the ability to drive automobiles in less than 30 minutes, preferably in about 15 minutes, or to allow substrates to be handled shortly after application of the adhesive system.